Author: Lizzie Smith – blog last updated on Wednesday 6th January 2024

In 85% of cases, the cause of bad breath lies in the mouth or throat. You can usually solve this yourself by paying more attention to your oral hygiene. It’s also a good idea to extend your oral hygiene routine to your tongue and, if necessary, also to your nose and tonsils.

bad breath stomach and intestines

However, a percentage of cases of bad breath will remain, the causes of which occur lower in the body. In this article, we’ll take a look at that.

Bad breath due to disorders in the stomach and intestines

Because our mouth is directly connected to our stomach and intestines, it’s not surprising that bad breath can also come from there. Some possible causes are:


When digesting food in the intestines, everyone releases gases. If the stool remains in the intestine for too long due to a blockage, it can ferment under the influence of intestinal bacteria. This releases sulphur gases, which enter the bloodstream through the intestinal wall. These gases are then exhaled through the lungs. This breath obviously doesn’t smell so good.

Imbalanced intestinal flora

Like the oral flora, the intestinal flora is a complex set of bacteria and other microbes that must keep each other in balance. Bacteria in the intestines are normal and even indispensable – they’re the ones that digest your food. However, the intestinal flora can become out of balance under certain circumstances. For example, due to a course of antibiotics, inadequate nutrition, caused whether or not by a strict diet.

You can usually correct these temporary imbalances by eating yoghurt, drinking kefir or other fermented milk products, or through probiotic supplements.

A poorly closing sphincter between the oesophagus and stomach

If the sphincter muscle doesn’t close the stomach properly, stomach acid and smelly gases can escape from the stomach. This is, for example, the case with people with a hiatal hernia. Nothing is broken, but the separation between the chest and abdomen, which the diaphragm serves, has become looser or wider over time. This condition, also called Sliding Hernia, is common. It’s estimated that 40 per cent of people over 60 suffer from it. Apart from bad breath and heartburn (reflux), it causes no further complaints.

The bacterium Helicobacter Pylori

The presence of this bacteria is associated with stomach cancer and stomach ulcers. Although Helicobacter Pylori doesn’t gain a lasting foothold in most people, it’s striking that people with it almost always suffer from bad breath. The Helicobacter Pylori bacteria in the stomach or intestines causes extra production of foul-smelling gases. If this is found after examination, antibiotics will be prescribed immediately.

A Zenker diverticulum

A Zenker diverticulum is a bulge in the oesophagus. It’s shaped like a pouch that hangs from the oesophagal wall. Food residues can remain in the bag through an opening in the oesophagal wall, which can rot, meaning a foul odour can come out of the mouth.

cure bad breath


Other conditions

Less common causes of bad breath that don’t come from the mouth or pharynx are severe liver or kidney diseases.

What should you do if you have bad breath from the stomach and intestines?

Unlike bad breath, the cause of which lies in the oral cavity, you can’t solve bad breath by yourself for some of the above reasons. You should see your doctor if the complaints persist despite good oral hygiene, a healthy diet, and normal digestion. They can then refer you to a dietician, an ENT (ear, nose and throat) specialist or a gastroenterologist.


British Dental Association:  Improving oral health

British Dental Journal: Help your patients tackle bad breath